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bruceo98
Samba Member
Joined: February 23, 2021
Posts: 716
Location: LA
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 Posted: Sat Dec 13, 2025 3:00 pm Post subject: Re: The DUNGBTL Build |
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Ok, I was just looking at my seats the other day on how I was going to mount them . This gives me a few ideas. But mine will have sliders . Looks good btw. Keep it up and you’ll be driving in no time.
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I may not be the best, but when the top 10 get together, they all talk about me. |
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DUNGBTL 
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Sat Dec 13, 2025 8:05 pm Post subject: Re: The DUNGBTL Build |
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| bruceo98 wrote: |
| Ok, I was just looking at my seats the other day on how I was going to mount them . This gives me a few ideas. But mine will have sliders . Looks good btw. Keep it up and you’ll be driving in no time. |
Thanks!
Made the mounting structure a couple years ago. Utilizes the factory mount. Started by making the rear floor mount…
The front mount attaches to existing holes in the factory front beam web…
The tops of the mounts are level side to side and front to back. Also, I engineered the seat mounting locns on the drivers side to move the seat inbd as far as possible to be better centered with the steering wheel. I believe I was able to move it 3/4” closer to the wheel centerline. Any more inbd, the seat bolster touched the ebrake handle. IIRC, the factory driver seat position was something like 1.5” outbd of the steering wheel centerline!
To react the seat overturning moment from clutching and braking, I tied the rear mount to the factory slider rails with gussets welded to the rails thus triangulating the mount…
It’s a bolt-in affair…solid, no discernible deflection/movement no matter how hard I leg press the firewall!
Got 3 lbs total out of the mounts by applying Drillium…
J. |
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Rome
Samba Member
Joined: June 02, 2004
Posts: 10839
Location: Pearl River, NY
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H2OSB
Samba Member
Joined: April 14, 2013
Posts: 1563
Location: Modesto, CA
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| Posted: Sun Jan 04, 2026 10:50 am Post subject: Re: The DUNGBTL Build |
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Outstanding! I've said it before and I'll say it again. You've added so much lightness, your car is going to float away.
H2OSB
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(o\_i_/o) Funny thing about pigs, they're cleaner than you and me. Well....you. |
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DUNGBTL
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Sun Jan 04, 2026 8:51 pm Post subject: Re: The DUNGBTL Build |
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 Thank you and a Happy New Year to you too!
Very cool! I wonder if it’s real…?
Notice the license plate…
Some other cars I really liked…
Thanks for the link Rome…that was fun!
J. |
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vwuberalles
Samba Member
Joined: October 18, 2003
Posts: 1529
Location: Richmond, VA
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DUNGBTL
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Mon Jan 12, 2026 5:55 pm Post subject: Re: The DUNGBTL Build |
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Polycarbonate windows V2.0
I decided to go full “race car” and mount polycarbonate windows directly to the window flanges, eliminating the window rubbers. This required ordering 3 more 0.118” thick polycarbonate sheets (TAP Plastics) to make new quarter and rear windows…
The window flanges measure 3/8” wide. To ensure adequate edge margin for the fastener holes in the plastic windows, I located the holes in the flanges 1/8” from the flange edge (or 1/4” from the body). This didn’t give a lot of room for edge margin in the plastic windows. Typically you want at least 2x the fastener hole diameter, or more, to help prevent stress cracks. To reduce the effects of stress concentration on the holes from thermal expansion of the polycarbonate, the fastener hole diameter should be several sizes larger than the fastener. To stay within recommended engineering guidelines, the fasteners had to be small in diameter.
I used 6-32 stainless machine screws. To help prevent stress cracks from thermal expansion, I used a “normal fit” hole diameter of 11/64” (.172”). To prevent over tightening, I used matching 6-32 domed sealing washers with bonded rubber…
The 11/64” hole (.172”) with a .25” edge distance yields a 1.5d edge margin (EM) which is not ideal but acceptable. Based on material thickness of .118”, the .172” hole yields a 2d EM which is good. All that aside, stress cracks may still form from the fastener holes after a few thermal cycles…especially the rear. Because the window opening is curved, the flat sheet of polycarbonate is under quite a bit of preload once pulled down to the curved opening…although that preload will probably be reduced when the temperature rises and the window expands. The window was installed at 52 degrees F. The quarter windows are flat. I’ll keep an eye out for stress cracks but I don’t think I’ll loose a window because of them.
I drilled and tapped the mounting holes for the 6-32 screws…
…the double layer window flange thickness measured 0.080” which was adequate for forming threads.
The fastener spacing was determined for the rear window by measuring the perimeter and dividing by a given number of fasteners until the spacing was even…33 fasteners, 3” spacing starting from the bottom center. An easier method was used on the quarter windows: locate the corners (3), then divide the distance between the upper fwd corner by 2, and then divide that half distance by 2 again. Same for the lower fwd corner. That yielded roughly 3.5-3.75” spacing and 21 fasteners.
I made all new templates because without the mounting rubbers, the windows need to be larger…
This time around, to cut the windows out from the sheet, I used a diamond grit metal cutoff wheel instead of an abrasive grit one… This worked even better as it didn’t melt the plastic…cleaner cutting.
I always cut slightly outside my template trace line and then ‘sneak’ up on the line using a disc sander and/or hand block.
I used 0.050” cardboard shims taped at the corners and vertical/horizontal centers to ensure the window was centered in the opening before I marked the fastener holes by going on the inside and marking thru the flange holes w/these cool “long reach nib markers”…
For the quarter windows, I cut a 3 1/4” diameter holes required for the PopIt Snap Vents. I used polycarbonate cleaner as the cutting lubricant which worked great! Super smooth/clean holes…
Before final mounting the windows, I painted a 5/8”-1/2” border on the inside of the windows around the fasteners. I used 1/4” 3M pin-stripe tape and followed a line drawn by a parallel edge marker tool I made…
I also blacked out both the outside and interior openings to mimic the ‘Cal-Look’ rubber look (which I like)…
Used SEM Trim Black…
For drilling the pilot holes in the windows I used a special pointy tip bit made for drilling plastics…
…enlarged the 1/8” pilot hole to 11/64 to allow room for fit-up and thermal expansion.
For sealing I used this 3/8” wide, ‘D’-shaped, foam rubber weatherstripping that has a sticky back and fits perfectly on the flange, not overhanging or squishing out…
It compresses down to ~1/8” although I purposely didn’t bottom out the windows in the openings to allow movement from thermal expansion.
Ok, so how much weight did I lose with all this nonsense? Here’s the tally:
-7 lbs for both quarter windows
-7 lbs for rear window
-5 lbs for the Cal-Look rubbers
A total of -19 lbs! And that’s weight from above the ‘belt line’ of the car so a bit more “effective” weight loss (lower CG).
J.
Last edited by DUNGBTL on Mon Jan 12, 2026 7:34 pm; edited 2 times in total |
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bruceo98
Samba Member
Joined: February 23, 2021
Posts: 716
Location: LA
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| Posted: Mon Jan 12, 2026 6:34 pm Post subject: Re: The DUNGBTL Build |
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That came out nice . You made the rear window or bought it curved? Really like the race car look . I’ve heard, don’t know if it’s true, that if you counter sink the drill hole it has less chance of cracking . Now you need the cal look door window trim to match.
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I may not be the best, but when the top 10 get together, they all talk about me. |
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DUNGBTL
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Mon Jan 12, 2026 7:17 pm Post subject: Re: The DUNGBTL Build |
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| bruceo98 wrote: |
| That came out nice . You made the rear window or bought it curved? Really like the race car look . I’ve heard, don’t know if it’s true, that if you counter sink the drill hole it has less chance of cracking . Now you need the cal look door window trim to match. |
Thanks!
I made all the windows from flat sheets of 0.118” abrasion resistant polycarbonate made in the USA. I deburred the fastener holes but did not countersink.
I’ve made poly ‘race’ windows before on another car using the same techniques I used here and had no stress cracks or other issues for the five years I had the car. However, the windows in that car did not have as much curvature as the beetle rear window has.
I found it interesting that once fully fastened, the rear window formed the compound curvature of the OEM glass. I can just barely detect a flat center section on close inspection. Before install, I was expecting a more concave appearance. We’ll see what it looks like when it’s in the sun and the ambient temperature is 110 F!  (“But it’s a dry heat!”  )
As far as the door windows go…I’m leaving them as is. They turned out looking like new and I don’t want to monkey with them. I have ‘Cal-look’ rubber for the windshield.
J. |
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vwuberalles
Samba Member
Joined: October 18, 2003
Posts: 1529
Location: Richmond, VA
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H2OSB
Samba Member
Joined: April 14, 2013
Posts: 1563
Location: Modesto, CA
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| Posted: Tue Jan 13, 2026 8:52 am Post subject: Re: The DUNGBTL Build |
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He cut the polycarbonate with clearance for thermal expansion. He won't have any issues with cracking until it gets old.
H2OSB
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(o\_i_/o) Funny thing about pigs, they're cleaner than you and me. Well....you. |
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Schepp
Samba Member
Joined: March 22, 2020
Posts: 827
Location: NorCal
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| Posted: Tue Jan 13, 2026 2:26 pm Post subject: Re: The DUNGBTL Build |
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This entire build is incredible. Its been fun watching this come together.
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Bandit #19
1972 Baja Rallycross Bug |
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DUNGBTL
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Thu Jan 15, 2026 12:11 pm Post subject: Re: The DUNGBTL Build |
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| bruceo98 wrote: |
| Now you need the cal look door window trim to match. |
I think I misunderstood/read your comment. I was thinking you meant polycarbonate door windows. 
You’re right and Mrs. DUNGBTL pointed out same. So I did just that. Did some precision masking of the brite work and window rubbers and gave the door windows a little black ‘eyeliner’…kinda like Keith Richards…subtle but I think it gives some continuity with the quarter window black out.
Thanks!
J. |
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DUNGBTL
Samba Member
Joined: October 17, 2022
Posts: 600
Location: Ashland, OR
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| Posted: Yesterday 5:46 pm Post subject: Re: The DUNGBTL Build |
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Well…this was satisfying! Two years in the waiting.
J. |
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